humanoid weld script not working correctly?

this script is supposed to weld all the children inside the model, which it does weld. But the problem is, sometime it welds weird, such as welding the left leg to the head or welding a part inside of the model where it supposed to be it welds it somewhere else. If you have other ways to approach this, please share

local prev 
local parts = script.Parent:GetChildren() 

for i = 1,#parts do 
    if (parts[i].className == "Part") or (parts[i].className == "WedgePart") or (parts[i].className == "UnionOperation") or (parts[i].className == "MeshPart") or (parts[i].className == "CornerWedgePart") then 
        if (prev ~= nil)then 
            local weld = Instance.new("Weld") 
            weld.Part0 = prev 
            weld.Part1 = parts[i] 
            weld.C0 = prev.CFrame:inverse() 
            weld.C1 = parts[i].CFrame:inverse() 
            weld.Parent = prev
        end 
        prev = parts[i]
        parts[i].Anchored = false
    end
end